FIGS. 1A-1H show simplified cross-sectional views of a conventional process for fabricating a package for a semiconductor device. The views of FIGS. 1A-H are simplified in that the relative proportions of the various components are not shown to the scale.
In FIG. 1A, a planar, continuous rolls 102 of conducting material such as copper, is provided.
In FIG. 1B, material is removed from regions of the planar roll 102 utilizing a chemical etching process. This chemical etching process involves forming a mask, and then etching in regions exposed by the mask, followed by removal of the mask. This chemical etching serves to define a central diepad 104 surrounded by a metal matrix 106. Although not shown in the particular cross-sectional view in FIG. 1B, portions of the diepad 104 may remain integral with the metal matrix 106.
FIG. 1C shows partial etching of the backside of portions of the patterned roll 102. Etched regions 104a of the periphery of the diepad 104 will later serve to allow the diepad to be physically secured within the plastic molding of the package body. Etched regions 108a correspond to portions of pins of the lead frame. These etched regions 108a will later serve to allow the pins to be physically secured within the plastic molding of the package body. FIG. 1C marks the step of completion of formation of lead frame 103.
FIG. 1D shows the formation of an electrically conducting adhesive material 110 on the die attach region 104b of the diepad 104. This electrically conducting adhesive material maybe comprise soft solder deposited in molten form. Alternatively, the electrically conducting adhesive material may comprise solder paste that is deposited in the form of small-sized particles of solder in a binder such as a solvent.
FIG. 1E shows the die-attach step, wherein the back side 112a of semiconductor die 112 is placed against electrically conducting adhesive material 110. As shown in FIG. 1E, one consequence of this die attach step may be the spreading of material 110 on the diepad 104 beyond the perimeter of the die 112.
FIG. 1F shows a subsequent step, wherein bond wires 114 are attached between contacts on the top surface 112b of the die 112 and pins 108.
FIG. 1G shows a further subsequent step, wherein the diepad 104, die 112, bond wires 114, and portions of the pins 108 are encapsulated with a plastic molding material 116 to define a body 118 of the package. As previously indicated, the recesses 104a and 108a serve to physically secure the diepad and pins, respectively, within the package during this encapsulation step.
FIG. 1H shows a subsequent singulation step, wherein the package 120 is separated from the surrounding metal frame by a sawing process.
While the conventional process flow just described is adequate to form a semiconductor device package, it may offer certain drawbacks. In particular, the partial etching step shown in FIG. 1C may be difficult to achieve, and hence adds to the cost of manufacturing the device. In particular, this partial etching step involves a number of steps, including the highly accurate patterning of a mask, followed by only partial etching in exposed areas and then removal of the mask. In particular, the partial etching of the metal roll may be difficult to halt with sufficient accuracy and repeatability.
Accordingly, there is a need in the art for a process for forming a semiconductor device package which avoids the need for a partial etching step.